The present invention relates to a method and a device for controlling an internal combustion engine with an air system.
A method and a device for controlling an internal combustion engine are discussed in German Patent No. 197 56 619. A system is described for operating an internal combustion engine, particularly in a motor vehicle, in which the air is supplied to a combustion chamber via a throttle valve arranged in an intake manifold, the quantity flow via the throttle valve being determined. At the same time, a valve is disposed in an exhaust-gas recirculation line, the quantity flow via the valve in the exhaust-gas recirculation line likewise being determined. The air-quantity flow into the combustion chamber is determined on the basis of the two air-quantity flows. Problematical in this device is that different variables needed for the calculation can only be acquired with difficulty using sensors. Therefore, it is disadvantageous that a large number of sensors are necessary for detecting the different variables.
The procedure of the present invention makes it possible to determine at least one variable which characterizes the air system. In so doing, only a few measured variables are necessary which are easily detectable using simple, inexpensive sensors. Furthermore, variables are used which are present internally in the control unit for controlling the internal combustion engine.
It is of particular advantage that the model includes at least one first and one second submodel, which determine output variables on the basis of input variables, besides at least one output variable of a second partial model, the manipulated variable and/or measured values being additionally considered as input variables of the first submodel.
The model building becomes particularly simple when, as the manipulated variable, the following are used: a fuel quantity ME which characterizes the fuel quantity to be injected, an exhaust-gas recirculation on/off ratio ATV which characterizes the control signal for an actuator influencing exhaust gas recirculation, and/or a supercharger on/off ratio LTV which characterizes the control signal for an actuator influencing the characteristics of a turbine. Preferably, besides the fuel quantity ME, the exhaust gas recirculation on/off ratio ATV and/or the supercharger on/off ratio are additionally used. This is done independently of whether the internal combustion engine is equipped with an exhaust gas recirculation system and/or a supercharger.
At least one speed variable (N) which characterizes the speed of the internal combustion engine, an ambient air temperature (T1) which characterizes the temperature of the ambient air, and/or an ambient air pressure (P1) characterizing the pressure of the ambient air are used as measured variables. The speed, the ambient temperature and the ambient pressure may be used.